Hi Jay,
If you are referencing the current open enrollment period, and your plan is satisfactory, then no you do not have to do anything, you will automatically continue in your current plan.
This is a problem I get calls about every day. If you have a true supplement plan like a plan F, G, N something like that these plans are what as known as Guaranteed Renewable. Basically there is no annual enrollment period for them. You can change them anytime of the year and as long as you pay the premium they can never be canceled and benefits do not change. The only reason to switch Supplemental programs would be because you can get a lower premium as the coverage is all the same.
If you are referring to the Medicare Advantage program (which most people call Supplements) then yes you should do a review every year. As long as your plan is not canceling the program for next year then you do not need to do anything. Just let it roll over to next year.